Understanding Macronutrients: Protein, Carbohydrates and Fats and How to Eat Them for Weight Loss

Updated: Mar 18

In this article:

  • What is protein and why is it important?

  • What are carbohydrates and why are they important?

  • What are fats and why are they important?

  • What should I eat when I am trying to lose weight?

  • How much protein should I eat?

  • How many carbohydrates should I eat?

  • How much fat should I eat?

  • How will I know how much of everything I am having?

  • If I am trying to lose weight, does it matter what sorts of macronutrients I eat to lose weight, as long as I stay within my calorie allowance?

  • What are good alternatives to make my calories go further?

  • I do a lot of exercise. What should I eat?

  • Examples of meals

  • Further reading

So you want to lose weight, and you know that it is important to eat a balanced diet of protein, carbohydrates and fats, (the macronutrients), but you need some help in choosing what to eat to stay within the limits you need to lose weight.

In this blog I will explain why having a good balance of the macronutrients is important for our health, and how we can use them to best effect to lose weight safely. I will try to keep things simple but will provide links where you can read further information. This blog is best read in conjunction with my other blog No BS: How to Lose Weight.

I will not be talking here about diets that restrict carbohydrates, that some people find very effective, as there simply isn’t the space to do it justice. That is for another day. So the main focus of this article is on safely losing weight while eating recommended proportions of the three macronutrients.

Please note this information is not aimed at people experiencing health problems such as insulin resistance or diabetes, or other health problems that affect what they can or should eat. Neither is it aimed at people with eating disorders. If any of these apply to you, please seek more specialist information and advice relating to your situation.

Before I go into the details, it's important to note that when we eat meals, we tend not to think of them as macronutrients in our minds, we just eat meals... and most foods contain combinations of the different macronutrients. We ideally need to aim to eat a good balance of all of them at every meal. I will go through the basics of what that means, and I appreciate this may seem a bit daunting but doing this really doesn't have to be complicated. Just taking a little time to learn about the subject really can make it much easier to choose what to have at any meal, and to become more aware of what might influence our success. It really will help you to make better choices for the rest of your life so is worth spending some time on.

However, I also appreciate it doesn't help when foods are described in different ways... eg the Eatwell Guide, which I talk about shortly, while very helpful, doesn't break things down in the same way as Myfitnesspal, so having an understanding of what macronutrients make up the different foods in the Eatwell Guide really can help. For example, are dairy products fat or protein? Are grains and pulses protein or carbs? The answer is they are both.

Reading the food labels and then seeing how they are represented graphically can really help get our heads around this. Apps like Myfitnesspal are very useful as you can look at the graphs as you input different foods, and see what the balance is across the macronutrients.

What is protein and why is it important?

There are many different proteins doing different jobs in our bodies, so strictly speaking we should really refer to them as proteins but it doesn’t really matter. It’s more important to know what they do.

Proteins are made up of basic building blocks called amino acids. Much of our bodies, both in terms of structures, substances, hormones and other chemical messengers that regulate our bodily functions, are made up from proteins, using the amino acids from the proteins that we eat in our food. We need proteins in our diets for growth and repair and to stay healthy.

Our bodies break down and build up proteins all the time. So if we don't get enough proteins in our diet, then it's clear to see why we might run into trouble with our health.

When reducing our calorie intake in order to lose weight it's really important to make sure we're still getting sufficient proteins, so that our bodies don't try to use too much of the proteins in our diet for energy thereby preventing them from doing all the other important things we need them to do. It also helps to keep us from getting too hungry.

There are 20 different amino acids that our bodies need. Some amino acids we can actually make in our bodies, so they are not essential, but others we have to get from our diet. For some of those amino acids that we make, we need to be in good health in order to do so, and not suffering illness or injury. At these times therefore it is especially important that we are eating enough proteins in our diet. We also need higher levels of protein, and energy intake, for recovery from illness and injury. That is not a time to try to lose weight, unless part of managing a weight-related health condition under the care of a doctor.

Some foods contain all the amino acids that we need, and these are usually animal sources. Other foods only contain some, and so it's important to choose from a variety to foods to ensure we are eating enough proteins to maintain good health, especially if we are following a vegan or vegetarian way of life.

Almost all natural foods contain some protein but the foods where protein is the highest macronutrient are things like meat, fish, seafood, eggs, soy, tofu and quorn. Lentils, beans and peas, whilst higher in carbohydrates, are still very good sources of protein for non-meat-eaters.

Please see the links at the end to read further about protein.

What are carbohydrates and why are they important?

Carbohydrates come in different forms... simple and complex, and are the main source of energy that our bodies use. The simpler the form, the easier it is for the body to use.

Simple carbohydrates are things like sugar, syrup, fruit juice concentrate.

Complex carbohydrates are known as starch, and these include things like bread, pasta, rice and potatoes, and they release energy more slowly - although there is a huge range to this according to how much fibre there also is in the food, and how processed it is. Also by adding protein and fat to carbohydrates in the form of a meal you can also help to slow down the release of energy. You may want to read about the Glycemic Index.

Then there are the non-starchy fibrous carbs...the non-starchy fruit and vegetables. These are all the things in the green section of the Eatwell Guide, and you really don't need to limit your quantities of these. They have great health benefits including slowing down our digestion, keeping our gut healthy and of course contain many of the vitamins and minerals that we need to sustain good health.

Please see the links at the end to read further about carbohydrates.

What are fats and why are they important?

Fats used to be seen as the enemy but it is now understood that fats are extremely important in our diet for good health. We just have to choose carefully and limit the quantities. There are different types of fats, some better for our health than others, but they ALL have 9 calories per gram.

Fats provide us with a large store of energy, make hormones, make up our brains and our cell membranes and they carry the very important fat-soluble vitamins to where they are needed in our bodies. So like protein, it is easy to see why we might run into trouble with our health if we don't get enough in our diets. Our bodies are continually building up and breaking down fats in order to use them

Fats are saturated, monounsaturated and polyunsaturated and we especially need the mono and polyunsaturated fats in our diets as they have particular properties that support our health.

Saturated fats are those which are solid at room temperature, such as butter, lard and cheese, while mono and polyunsaturated fats are liquid at room temperature, such as oils. Fats are also found in varying quantities in many unprocessed foods high in protein; we tend not to eat many fats on their own, we usually use them for cooking, spreading, dressing and topping. Cutting these down or out is an easy way to cut down on calories without changing too much else.

Please see the links at the end to read further about fats.

What should I eat when I am trying to lose weight?

It depends what weight loss approach you are following, but if you are simply trying to reduce your energy intake and eat a balanced diet, and are not doing extreme activities like bodybuilding, then in my experience you want to aim for about 45-65% of your calories to come from carbohydrates, 15-35% from protein, and 20%-30% from fats. Figures from different sources vary. But it does not need to be exact, and we do not need to get hung up on the numbers.... these are very rough proportions. As long as you are choosing from the various food groups according to the proportions in the EatWell Guide below, then you will be doing alright.

How much protein should I eat?

Proteins contain 4 calories per gram, but the body will use them for all the reasons described above before it will use them for energy. Most sedentary adults in good health need about 1g of protein per kg of bodyweight, so a 140 pound /10 stone/63kg woman doing little exercise would need around 63g of protein per day, on average. This is achievable on a balanced diet by having 1 palm sized portion of protein at main meals and including some protein in 1-2 snacks per day. So this could consist of porridge for breakfast, tuna or cottage cheese at lunchtime and chicken breast or tofu at dinner time and some nuts and greek yogurt at 2 snacks.

The more active we are, or if we are ill or injured, the more protein we need. Protein also helps us to keep fuller for longer, which can help with managing hunger when trying to lose weight, and also helps us to preserve our lean tissues. If you are not sure how much to have, it's better to aim for more than less, especially if you are very active. The body will get rid of any amino acids it doesn't need but may use the excess protein as energy so it's important to still stay in a calorie deficit to lose weight. There are varying reports on whether too much protein is harmful or not, but if in a calorie deficit it will be very difficult to have too much. See below for more.

How many carbohydrates should I eat?

Carbohydrates contain 4 calories per gram, the same as protein. General advice is that our diet should be highest in carbohydrates but care needs to be taken as to what they consist of. Aiming for minimally processed forms, high in fibre most of the time is ideal, not just in terms of giving us longer lasting energy and helping to control insulin problems, but also in terms of the micronutrients (the vitamins and minerals) that they contain. This also gives us a greater volume of food for the calories consumed and helps to keep us fuller for longer. Any excess carbohydrates consumed will be stored first in the liver and muscles, as glycogen, for energy, and then as fat. See below for more. As mentioned previously, please note this information is aimed at people not suffering any health problems such as insulin resistance or diabetes, who will need more specialist advice.

How much fat should I eat?

Fats contain 9 calories per gram, over twice that of protein and carbohydrates. Fat should ideally take up no more than 20% - 30% of our calorie intake, with the majority of that coming from mono and polyunsaturated fats. See below for more.

How will I know how much of everything I am having?

If you are just getting started, using the Eatwell Guide can be really useful. Print it off, study it, get to know it.

If you are not used to managing portions or feel you need to get to know more about the foods you are eating, including how much energy is in them, then you could build on this by using a tracker like Myfitnesspal.

Then there is the hand portion guide, which very basically, for each main meal, is:

  • 1 palm-sized portion of protein rich food eg meat, fish, tofu, 2 eggs etc

  • 1 cupped palm of carbohydrate rich food eg potatoes, pasta, rice, peas, beans,

  • 2 cupped palms of non-starchy fibrous fruit and vegetables

And optionally

  • 1 thumb of fats eg butter, hard cheese, oil, cream, bearing in mind most foods containing protein also contain fats this may not be necessary, depending on what else you are eating.

As our hand sizes tend to vary according to our own size, and are easily accessible for measuring, this is a very quick and easy way to keep control of portion sizes. We can adjust upwards according to our needs- men or extremely active women may need up to to two of each serving. You can play around with it and see what happens to your weight to find out what you need.

I would also highly recommend downloading and printing this excellent article from Precision Nutrition https://www.precisionnutrition.com/what-should-i-eat-infographic.

If I am trying to lose weight, does it matter what sorts of macronutrients I eat to lose weight, as long as I stay within my calorie allowance?

Yes it does... quality is just as important as quantity. As I have explained in my blog posts No BS How to Lose Weight and An Introduction to Emotional Eating, amongst others, when we eat heavily processed foods, which tend to be higher in saturated fat, refined sugar, and salt, our bodies digest them quickly and easily and we crave more of them, which makes us want more... making it so much harder to stick to any programme. They are also thought to be linked to various health problems.

So not only does this introduce things into our bodies that we're not very well-equipped to deal with, and don't make us feel that great, we also don't get much 'bang for our buck', and the body digests them really quickly so we don't stay full for long and can quickly feel hungry or have cravings again soon after, and often give in to them. This does no good for our confidence in our ability to lose weight.

So always aim to choose foods that are as close to their natural state as possible, and avoid adding extra sugar. Eg rolled porridge oats with some dried fruit rather than adding sugar or syrup to sweeten it. Frozen and tinned foods are fine if they are still in their original form.

What are good alternatives to make my calories go further?

A quick search on google or Pinterest will give you lots of ideas but here are a few:

  • Change white rice to brown or wild rice, or cauliflower rice

  • Change white potatoes (including chips and mashed potatoes) to carrot and swede mash, or sweet potatoes

  • Change regular pasta to whole-wheat pasta, or spiralised vegetables such as courgette

  • Change white bread to whole-wheat or whole-grain bread

  • Change sugary breakfast cereals to high fibre, low-sugar cereal like oats, or have eggs for breakfast instead

  • Change crisps to small flat palm of nuts, or nibble on carrot sticks

  • Change ice cream to Greek yogurt and fruit

  • Change chocolate bar to banana and small flat palm of unsalted nuts.

  • Change milk chocolate to dark chocolate - it's harder to eat as much!

  • Change cream to creme fraiche

I do a lot of exercise. What should I eat?

When it comes to exercise, food is fuel, and the higher the quality the better. You wouldn't put low quality fuel into a high performance sports car, or not put any fuel in it, and then expect it to work properly, so think of your body in the same way.

Make sure your diet is high in good quality protein and carbohydrate sources at all times, eat well in the hours before exercising, with a combination of complex carbs but allow a good 2 hour gap to digest what you have eaten. While it is possible to exercise on a diet low on carbohydrates, bear in mind that performance is likely to be affected.

Try to eat a meal high in both protein and carbohydrates as soon as possible after exercising, to replenish your body's glycogen stores and to enable your muscles to repair themselves, promoting a faster recovery. Protein shakes and bars are handy for convenience but not essential unless you are undertaking an intensive training regime. They can be loaded with sugar too, so make sure you read the labels if you choose to have these.

It takes the body a long time to digest fat, so it's not ideal to eat foods high in fat before exercise as it may not be a very enjoyable experience.

Examples of meals

Here are a couple of examples of my own balanced, far from perfect, but ok, diet. One day represents convenience and the other day represents cooking dinner from scratch. I am the first to admit I am not very inventive when it comes to cooking and recipes. I prefer to keep things very simple, but there are some great websites out there such as Pinch of Nom that can help you.

Please note the change in fat and protein % between the two days. I show you this to illustrate that a single day's change in balance won't make any difference, as long as the balance over time is within the ideal range.

Each meal has a balance of all nutrients with the exception of the banana in the morning snack on day 2. Some food is processed, some is unprocessed. On both days I am in a calorie deficit, in that I am eating less calories than my body needs, in order to demonstrate an example of how it can be done while eating a mix of mainly unprocessed foods and a small proportion of treats.



Quaker - Oat So Simple Pot, 45 g

Half a pack of Whitworth's - Berry & White Chocolate Shot, 12.5 g


Morrisons - British Shorthorn Steak Pie, 132 grams

Birds Eye - Steam Fresh Family Favourite Mix, 135 gram

Afternoon Snack

Other half of Whitworth's - Berry & White Chocolate Shot, 12.5 g

Tesco - Mixed Nuts and Raisins, 25 g


Morrisons Savers Macaroni Cheese, 400 g

Peas 80 g


Semi-Skimmed Milk, 300ml for use in tea and coffee

Total calories 1550 approx

Day 2:


Fuel 10k - porridge golden syrup , 70 gram

Morning Snack

Banana - (Small)


Egg, 2 large

Wholemeal muffin

100% peanuts Peanut Butter Crunchy, 10 g

Green Salad - Green Salad,

50g Lindt - 90% Cocoa, 10 g


Morrison - Chicken Breast Fillet, 182 g

potatoes - new Boiled, 120 g

Carrot - 1 Medium Size, 61 g

Cauliflower, 1 cup, chopped

Bisto - Gravy, 150 ml

Cranberry sauce, 10 g

Rich tea - Biscuit, 2 piece


Skimmed milk 400 ml

Magnum Mini - Double Caramel, 1 bar (54 ml)

Total calories 1650 approx

If you found this helpful why not check out my top 10 tips for eating less without dieting, for some tips on how to manage your food intake in general.

If you need a bit more support why not check out my e-book, Preparing for Successful Weight Loss, where I cover all the things that need to be in place to lose weight and keep it off, and help you uncover what might be holding you back and overcome it.

Further reading

BNF : A Healthy Balanced Diet

PN: When and how much to eat PN:What should I eat?

Wikipedia: About protein

Wikipedia: About carbohydrates

NHS: About fats

NHS: The Glycemic Index Pinch of Nom calorie counted recipes

Healthline: Can you eat too much protein?

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